(a) Field of the Invention
This invention relates to a method of manufacturing an electrochromic display cell comprising a cover soldered to a substrate.
The invention also relates to an electrochromic display cell.
(b) Description of the Prior Art
Due to their low current consumption, electrochromic display cells are specially well suited for use in portable apparatus powered by a battery of low capacity, such as, for example, electronic watches.
Sealing of the cover or cap of these cells to their substrate is effected by soldering, for instance by means of a eutectic tin-head alloy solder, the cover being metallic and the substrate, made of glass, comprising a metallized sealing frame. This is at present the type of sealing of the cover which gives the best results so far as the effectiveness of the seal with respect to oxygen and steam is concerned. SUMMARY OF THE INVENTION
The drawback of this method lies in the fact that the contact between the solder and the ionic conductor of the cell can produce chemical reactions conducive to contamination of the ionic conductor and to corrosion of the solder. The object of the present invention is to overcome this drawback.
Generally speaking, in accordance with the invention, the manufacturing of an electrochromic display cell is disclosed, comprising the steps of
providing a first enclosing element comprising a cover including a substantially flat peripheral portion and a first annular soldering means disposed on said peripheric portion;
providing a second enclosing element comprising a substantially flat substrate including a second annular soldering means disposed on said substrate and having a shape adapted to the shape of said first soldering means, at least an electrode disposed on said substrate at least partially within said second soldering means, electrochromic material disposed on at least a portion of said electrode within said second soldering means;
providing a protective frame adapted to surround said electrode and to be in contact with said cover and said substrate when located within said first and second soldering means placed in a facing relationship;
providing an ionic conductor;
mounting said enclosing elements, said frame and said ionic conductor in a relative position such that said first and second soldering means are in a facing relationship, said frame is located between said cover and said substrate within said first and second soldering means and surrounding said electrode, and said ionic conductor is located within said frame between said electrochromic material and said cover;
applying a force on said enclosing elements after said mounting to squeeze said frame between said cover and said substrate; and
sealing together said first and second soldering means during said application of a force.
An electrochromic display cell is also disclosed, which comprises the step of depositing said frame by screen-printing.
The protective frame so provided in the cell prevents any contact and, thus, any chemical reaction between the soldering means and the ionic conductor.
The various features of the invention will be apparent from the following description, drawings and claims, the scope of the invention not being limited to the drawings themselves as the drawings are only for the purpose of illustrating a way in which the principles of the invention can be applied. Other embodiments of the invention utilising the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appendant claims.